This invention relates to the fabrication of microminiature devices such as integrated circuits and, more particularly, to the delineation of fine-line patterns in such devices by dry etching processes.
Considerable interest exists in employing dry processing techniques for patterning workpieces such as semiconductor wafers. The interest in such techniques stems from their generally better resolution and improved dimensional and shape control capabilities relative to standard wet etching. Thus, dry etching is being utilized increasingly for pattern delineation in the processing of, for example, semiconductor wafers to form large-scale-integrated (LSI) devices.
Various dry etching processes that involve the use of gaseous plasmas are known, as described, for example, in "Plasma-Assisted Etching for Pattern Transfer" by C. J. Mogab and W. R. Harshbarger, Journal of Vacuum Science and Technology, 16(2), March/April 1979, p. 408. As indicated therein, particular emphasis in recent work has been directed at developing processes that utilize reactive gas plasmas in a mode wherein chemical reactions are enhanced by charged particle bombardment.
Considerable effort has been directed recently at trying to devise reliable plasma etching processes for fine-line pattern delineation in silicon surfaces. Of particular practical interest has been the work directed at etching polysilicon. Polysilicon films, both doped and undoped, constitute constituent layers of commercially significant LSI devices such as 64K dynamic random-access-memories (RAMs) of the metal-oxide-semiconductor (MOS) type. Accordingly, it was recognized that improved methods of patterning silicon by plasma etching, if available, could contribute significantly to decreasing the cost and improving the performance of such devices and other structures that include silicon substrates or layers.